Problem: Evaluate the following expression when $d = 6$ and $c = 10$. $9$ $d$ $ + 8$ $c$ $ + 4$
Solution: Substitute $6$ for ${d}$ and $10$ for ${c}$ $ = 9{(6)} + 8{(10)} + 4 $ $ = 54 + 80 + 4 $ $ = 138$